Question: My friend reads three times as fast as I do. If it takes me 2 hours to read a novella, how many minutes will it take my friend to read the same novella?
In reading, $\text{speed}=\frac{\text{amount of material}}{\text{time}}.$ Let the amount of material in the novella be $N.$ So $\text{speed}=\frac{N}{\text{time}}.$
Also, it is a good idea to convert hours to minutes since the answer should be in minutes: $2hrs=2\cdot 60min= 120min.$
Knowing that my friend reads three times as fast as I do, we can set up a proportion of our speeds: $$\frac{\text{my friend's speed}}{\text{my speed}}=3.$$And now we can use the formula above to proceed. \begin{align*}
\frac{\text{my friend's speed}}{\text{my speed}}&=3\\
\frac{\frac{N}{\text{my friend's time}}}{\frac{N}{120\text{ min}}}&=3\\
\frac{N}{\text{my friend's time}}\cdot\frac{120\text{ min}}{N}&=3\\
\frac{N\cdot 120\text{ min}}{\text{my friend's time}\cdot N}&=3\\
\frac{120\text{ min}}{\text{my friend's time}}&=3\\
\text{my friend's time}&=\frac{120\text{ min}}{3}\\
\text{my friend's time}&=\boxed{40\text{ min}}.
\end{align*}